Keratosis senilis; a biologic concept of its pathogenesis and diagnosis based on the study of normal epidermis and 1730 seborrheic and senile keratoses

Bowen disease is not synonymous with intraepidermal squamous cell carcinoma

The terms 'Bowen disease' and 'intraepidermal squamous cell carcinoma' are sometimes considered synonymous. In this paper we present historical, clinical, histological and molecular evidence that this is incorrect. The term Bowen disease should be reserved for a subset of intraepidermal squamous cell carcinoma with a distinctive and reproducible morphological pattern, described in detail by Bowen in 1912. One other common subset of intraepidermal squamous cell carcinoma represents progression of actinic keratosis. In some cases the separation of these two common patterns of intraepidermal squamous cell carcinoma can be challenging and there are patterns of intraepidermal squamous cell carcinoma which appear to represent other distinct pathways. However, there is emerging biological evidence to support this distinction and reason to suspect that the types of invasive squamous cell carcinoma which arise from these different pathways may show important clinical and biological differences, particularly in the era of targeted and immunomodulatory therapy for advanced disease.

In-Vivo LC-OCT Evaluation of the Downward Proliferation Pattern of Keratinocytes in Actinic Keratosis in Comparison with Histology: First Impressions from a Pilot Study

It is known that actinic keratoses (AKs) can progress to invasive squamous cell carcinoma (SCC). The histological PRO grading of AKs is based on the growth pattern of basal keratinocytes and relates to their progression risk. AKs can be non-invasively characterized by line-field confocal optical coherence tomography (LC-OCT). The aim of the study was to define criteria for an LC-OCT grading of AKs based on the PRO classification and to correlate it with its histological counterpart. To evaluate the interobserver agreement for the LC-OCT PRO classification, fifty AKs were imaged by LC-OCT and biopsied for histopathology. PRO histological grading was assessed by an expert consensus, while two evaluator groups separately performed LC-OCT grading on vertical sections. The agreement between LC-OCT and histological PRO grading was 75% for all lesions (weighted kappa 0.66, 95% CI 0.48-0.83, p ≤ 0.001) and 85.4% when comparing the subgroups PRO I vs. PRO II/III (weighted kappa 0.64, 95% CI 0.40-0.88, p ≤ 0.001). The interobserver agreement for LC-OCT was 90% (Cohen's kappa 0.84, 95% CI 0.71-0.91, p ≤ 0.001). In this pilot study, we demonstrated that LC-OCT is potentially able to classify AKs based on the basal growth pattern of keratinocytes, in-vivo reproducing the PRO classification, with strong interobserver agreement and a good correlation with histopathology.

Actinic keratoses - a systemic review

Mainly elderly people with pale skin are affected by actinic keratoses (AK). Due to the demographic change, the prevalence of AK increased over the last years. An established risk factor is chronic UV-exposure (outdoor workers) inducing mutations of the tumor suppressor gene TP53 and the oncogene H-Ras. This leads to an intraepidermal proliferation of atypical keratinocytes. The term “field cancerization” characterises the presentation of multiple AK in UV-exposed areas. AK are also termed squamous cell carcinoma (SCC) in situ. The risk for AK turning into a SCC is 6-10%. In order to avoid invasive growth, an early treatment is recommended. During the last years multiple therapeutic options have been established. Depending on the clinical extent, lesion- or field-directed therapies with excellent clinical response and cosmetic results are available.

Differentiation of benign pigmented skin lesions with the aid of computer image analysis: a novel approach

BACKGROUND

The differential diagnosis of common pigmented skin lesions is important in cosmetic dermatology. The computer aided image analysis would be a potent ancillary diagnostic tool when patients are hesitant to undergo a skin biopsy.

OBJECTIVE

We investigated the numerical parameters discriminating each pigmented skin lesion from another with statistical significance.

METHODS

For each of the five magnified digital images containing clinically diagnosed nevus, lentigo and seborrheic keratosis, a total of 23 parameters describing the morphological, color, texture and topological features were calculated with the aid of a self-developed image analysis software. A novel concept of concentricity was proposed, which represents how closely the color segmentation resembles a concentric circle.

RESULTS

Morphologically, seborrheic keratosis was bigger and spikier than nevus and lentigo. The color histogram revealed that nevus was the darkest and had the widest variation in tone. In the aspect of texture, the surface of the nevus showed the highest contrast and correlation. Finally, the color segmented pattern of the nevus and lentigo was far more concentric than that of seborrheic keratosis.

CONCLUSION

We found that the subtle distinctions between nevus, lentigo and seborrheic keratosis, which are likely to be unrecognized by ocular inspection, are well emphasized and detected with the aid of software.

Minichromosome maintenance protein expression according to the grade of atypism in actinic keratosis

The minichromosome maintenance (MCM) family is a group of proteins that are key initiation factors for DNA replication and are expressed only in cycling cells. Recent studies on various cancerous conditions have shown that MCM proteins are better markers for malignant cells compared to other proliferative markers. It has been also proven that MCM proteins are independent prognostic factors. The aim of this study was to characterize the pattern and frequency of MCM 2 protein expression in actinic keratosis (AK) and determine whether the expression is correlated with the degree of histological atypism. Biopsy samples of 34 patients who had been diagnosed as AK were used in this study. Samples were divided into three groups (grade I, grade II, and grade III) according to the degree of atypism. Immunohistochemical staining for MCM 2 protein, Ki-67, and proliferating cell nuclear antigen was performed, and the number of positively staining cells per unit area (10⁻⁴ μm²) was calculated for evaluation of immunoreactivity. MCM 2 protein was expressed in atypical keratinocytes in AK. Mean numbers of immunoreactive cells positive for MCM 2 were 165.1 in grade I, 304.5 in grade II, and 513.3 in grade III. Moreover, the correlation between the immunoreactivity for MCM 2 protein and AK grade was significantly more positive than that for other markers. Thus, we suggest that MCM 2 protein is a reliable marker for diagnosing and grading AK and further could be hypothesized as an important prognostic factor.

Malignant skin neoplasms

Skin cancers may be derived from any part of the skin, and the classification of all variants is extensive. Overall they are the most common cancers of the body, and include those that are highly mortal and those that are associated with an increased morbidity. In this review the most common skin cancers confronted by the clinician and their management are discussed. New associations are highlighted, as well as new information that can help the clinician to better understand the pathogenesis of many of these entities.

Actinic keratosis is an early in situ squamous cell carcinoma: a proposal for reclassification

The term actinic keratosis (AK) describes a sun-induced, clinical erythematous lesion covered with scale, but does not provide an understanding of the biology or histopathology of the lesion. Consequently, several classification systems for AK have been suggested, but as yet no consensus has been reached. These systems strive to correlate the pathological and clinical features to better provide physicians with the most accurate information to enable correct decisions to be made regarding treatments, Prognosis and metastatic potential. AK is a clinical description that has a histological diagnosis consistent with squamous cell carcinoma (SCC) in situ. We recommend an AK classification system that describes these lesions as squamous cell carcinomas (SCCs), using the terminology 'early in situ SCC Type AK I', 'early in situ SCC type AK II' and 'in situ SCC Type AK III', there by giving clinicians better guidance for diagnosis and specific treatment recommendations.

Correlation between Bcl-2 and Bax in atrophic and hypertrophic type of actinic keratosis

BACKGROUND

Recent investigations consider actinic keratosis (AK) as an earliest visible pattern of squamous cell carcinoma (SCC). We have analysed the expression of apoptosis-related proteins TP53, Bcl-2 and Bax in 30 atrophic and 30 hypertrophic AK cases.

MATERIAL AND METHODS

Immunohistochemical analysis was performed following microwave streptavidin immunoperoxidase protocol on DAKO TechMate Horizon automated immunostainer (DAKO, Copenhagen, Denmark). Monoclonal antibody for TP53 and Bcl-2 and polyclonal antibody for Bax (DAKO, Copenhagen, Denmark) were used.

RESULTS

Expression of TP53 showed no significant differences between two analysed groups (chi2-test, P = 0.35636) whereas expression of Bcl-2 and Bax protein was significantly higher in atrophic compared to hypertrophic AK (chi2-test, P = 0.01458 and P = 0.00358, respectively). Comparison of Bcl-2 : Bax ratio in two analysed AK showed significantly higher value in hypertrophic compared to atrophic AK (Mann-Whitney U test, P = 0.02272). Statistical analysis did not show any correlation between patient's sex and age, localization and size of the lesion with expression of investigated oncoproteins (anova, P > 0.05).

CONCLUSIONS

Our results may indicate higher resistance of keratinocytes on apoptotic stimuli in hypertrophic compared to atrophic AK. Thus, we suppose that keratinocytes in hypertrophic AK live longer and probably have higher propensity for additional mutations and conversion to overt SCC.

[Solar keratosis: from precancerous lesion to pre-invasive squamous cell carcinoma--therapeutic approach with a bioinductive method]

BACKGROUND

Solar keratoses are precancerous lesions in chronically UV-damaged skin with histological features consistent with pre-invasive squamous cell carcinoma. They require therapeutic intervention in order to prevent progression towards invasive carcinoma. Treatment options include topical medications and destructive methods. We report on a new approach--topical bioinductive therapy with imiquimod 5% cream.

PATIENTS AND METHODS

In a prospective case series, 7 patients with solar keratoses have been treated with topical imiquimod 5%. The cream was applied 5 days/week over 2 weeks. After end of treatment, the outcome was assessed at regular control visits and, in some cases, histologically confirmed. One patient was followed up as untreated control.

RESULTS

In 6 of the 7 treated patients, the lesions cleared completely; one patient did not respond. The patients did not show new solar keratoses during a follow-up period of about 2 years. The untreated patient showed spontaneous clearance of his keratoses. Local skin reactions during treatment included erythema, oedema and erosions in varying degrees, all of which completely resolved.

CONCLUSIONS

Bioinductive therapy with imiquimod 5% cream represents a promising therapeutic approach for cutaneous precancerous lesions such as solar keratoses.

Interpreting epithelial cancer biology in the context of stem cells: tumor properties and therapeutic implications

Over 90% of all human neoplasia is derived from epithelia. Significant progress has been made in the identification of stem cells of many epithelia. In general, epithelial stem cells lack differentiation markers, have superior in vivo and in vitro proliferative potential, form clusters in association with a specialized mesenchymal environment (the 'niche'), are located in well-protected and nourished sites, and are slow-cycling and thus can be experimentally identified as 'label-retaining cells'. Stem cells may divide symmetrically giving rise to two identical stem cell progeny. Any stem cells in the niche, which defines the size of the stem cell pool, may be randomly expelled from the niche due to population pressure (the stochastic model). Alternatively, a stem cell may divide asymmetrically yielding one stem cell and one non-stem cell that is destined to exit from the stem cell niche (asymmetric division model). Stem cells separated from their niche lose their stemness, although such a loss may be reversible, becoming 'transit-amplifying cells' that are rapidly proliferating but have a more limited proliferative potential, and can give rise to terminally differentiated cells. The identification of the stem cell subpopulation in a normal epithelium leads to a better understanding of many previously enigmatic properties of an epithelium including the preferential sites of carcinoma formation, as exemplified by the almost exclusive association of corneal epithelial carcinoma with the limbus, the corneal epithelial stem cell zone. Being long-term residents in an epithelium, stem cells are uniquely susceptible to the accumulation of multiple, oncogenic changes giving rise to tumors. The application of the stem cell concept can explain many important carcinoma features including the clonal origin and heterogeneity of tumors, the occasional formation of tumors from the transit amplifying cells or progenitor cells, the formation of precancerous 'patches' and 'fields', the mesenchymal influence on carcinoma formation and behavior, and the plasticity of tumor cells. While the concept of cancer stem cells is extremely useful and it is generally assumed that such cells are derived from normal stem cells, more work is needed to identify and characterize epithelial cancer stem cells, to address their precise relationship with normal stem cells, to study their markers and their proliferative and differentiation properties and to design new therapies that can overcome their unusual resistance to chemotherapy and other conventional tumor modalities.

The diagnostic concordance of actinic keratosis and squamous cell carcinoma

Diagnostic concordance of intraepithelial malignancy is generally only fair. Because the diagnosis of actinic keratosis (AK) and squamous cell carcinoma (SCC) is not uniform and because such terms are not consonant with the nomenclature of other human epithelial malignancies, nomenclature revisions have been attempted. One hundred dermatopathologists were solicited to review 15 tissue sections representing a spectrum of varying thickness epidermal malignancy and to choose either AK or SCC as the diagnosis. Among the 77 participating dermatopathologists, intraclass correlation was high for what was perceived as AK, SCC, and their differentiation. Development of a two-tiered diagnostic system that retains our present diagnostic capabilities, but better fits the pathobiology of superficial epidermal malignancy is suggested. Davis DA, Donahue JP, Bost JE, Horn TD. The diagnostic concordance of actinic keratosis and squamous cell carcinoma.

Premalignant and early squamous cell carcinoma

Actinic keratosis (AK) is a common sun-induced precancerous neoplasm confined to the epidermis. The AK is the initial manifestation of a continuum of clinical and histologic abnormalities that progresses to invasive squamous cell carcinoma (SCC). Bowen's disease, also known as squamous cell carcinoma in situ, represents early SCC confined to the epidermis. More than half of all SCCs contain p53 tumor suppressor gene mutations. Like SCCs, the vast majority of AKs and Bowen's disease lesions are asymptomatic. Each AK and suspicious lesion should be treated before it progresses to invasive SCC. Destructive modalities, such as cryosurgery using liquid nitrogen and electrodesiccation and curettage, usually performed by a dermatologist, are the mainstays of therapy.

Gene expression in actinic keratoses: pharmacological modulation by imiquimod

BACKGROUND

Actinic keratoses (AKs) are premalignant lesions that can progress into squamous cell carcinoma. Imiquimod, which belongs to the new class of immune-response modifiers, was recently shown to be effective in the treatment of AKs. The underlying mechanisms are not fully understood.

OBJECTIVES

To study the expression of individual genes in uninvolved skin and AKs before therapy and to elucidate the way in which the expression of these genes is influenced by imiquimod therapy.

METHODS

We treated 13 patients with AK with imiquimod and compared gene expression before, during (five patients) and after (eight patients) therapy with that in uninvolved skin. We analysed genes coding for inflammatory cytokines or their receptors, adhesion molecules, anti-apoptotic proteins, p53 and toll-like receptors (TLRs) by reverse-transcriptase polymerase chain reaction.

RESULTS

Comparing uninvolved skin and untreated AK, we found significant differences in the expression of interleukin (IL)-6, hurpin, TLR7 and TLR8. During imiquimod therapy, we detected a further upregulation of interferon-alpha, IL-6, IL-10 receptor 1 and TLR7. In contrast, two anti-apoptotic genes, hurpin and HAX-1, were downregulated. We did not detect significant differences in gene expression for p53, tumour necrosis factor-alpha and alpha- and beta-catenins. Clinically, the upregulated expression of the proinflammatory cytokines correlated with the local inflammation induced by imiquimod.

CONCLUSIONS

Our results indicate that specific differences in gene expression are detectable between AK and uninvolved skin. Imiquimod influenced the expression of most genes analysed in this study. This work extends previous findings on the effects of imiquimod on gene regulation in AKs.

[Actinic keratoses]

Actinic keratoses are defined as proliferation of cytologically atypical keratinocytes in the zone of epidermal-dermal junction in photodamaged skin. In the northern hemisphere the prevalence of actinic keratoses ranges depending on different epidemiological studies from 11% to 25% for people aged 40 or older. The main cause of actinic keratoses is exposure to UVB radiation in sunlight UVB radiation induces mutations in the telomerase gene and in the tumor suppressor gene P53, which can also be detected in invasive squamous cell carcinoma. The only histological parameter to distinguish between actinic keratoses and SCC is the level of invasiveness. The risk for actinic keratoses to develop into SCC is about 16% over lo years. For this reason and because of the high prevalence of actinic keratoses, it has been suggested to replace the term,, actinic keratosis K with intraepidermal squamous cell carcinoma' to better characterize the lesion. In the following review recent aspects of pathogenesis and therapy of actinic keratoses are discussed.

Histopathology of incipient intraepidermal squamous cell carcinoma ("actinic keratosis")

BACKGROUND

Actinic keratoses (AKs) are proliferations of transformed, neoplastic keratinocytes confined to the epidermis induced by exposure to ultraviolet (UV) radiation in sunlight. They are extremely prevalent and are seen in most middle-aged to elderly Caucasian persons with a history of significant sun exposure. These lesions are currently termed AKs while they remain confined to the epidermis, but when they extend more deeply to involve the papillary and/or reticular dermis, they are termed squamous cell carcinoma (SCC). The term AK was developed on the basis of clinical appearance and texture of these lesions without regard to histopathology or pathobiology.

METHODS

This study was based on a current and historical literature review.

RESULTS

AKs and SCC represent the same disease process at different stages of evolution. Neoplastic transformation occurs in keratinocytes exposed to UV radiation manifest primarily as mutations in the p53 gene. In time, these cells proliferate in the epidermis and eventually extend into the dermis at which point metastatic spread can occur. Cytologic atypia is visible in early stages and is identical to that seen in SCC that is present in the dermis or in metastatic lesions. This sequence of events is directly analogous to that of evolving carcinoma of the uterine cervix that has been termed cervical intraepithelial neoplasia.

CONCLUSION

AKs are malignant neoplasms in evolution and demonstrate histologic and molecular genetic features of malignancy. Because the name currently used to describe these lesions does not reflect the pathobiology of the process, we propose that a new, more appropriate name be given to these lesions. We propose that a classification scheme analogous to that used by gynecologists for evolving carcinoma of the uterine cervix using the terminology "keratinocytic intraepidermal neoplasia" or another term such as "solar keratotic intraepidermal SCC" be used to define these lesions and that the term actinic (solar) keratosis be eliminated.

Basosquamous carcinoma after ultraviolet therapy with artificial sunlight

We report a 63-year-old Japanese man with basosquamous carcinoma developing after ultraviolet therapy with artificial sunlight. Because he had had an eczematous lesion on the right leg five years previously, he had received ultraviolet therapy with artificial sunlight from a mercury-quartz lamp for a total of 30 sessions over a 3-year period. Physical examination revealed an irregular erythematous plaque measuring 5 x 6 cm, with slight eruptions and erosions, on the right leg. A brownish plaque, measuring 9 x 12 cm, surrounded the erythematous plaque. Histopathologically, in the nests of atypical cells in the dermis, nuclear palisading was present at the edge of each tumor cluster. Adjacent clusters exhibited transitions to squamous cells and contained horn pearls. Most of the cells of the epidermis and adnexa were atypical, but cells of the normal adnexal epithelium extended over the atypical cells of the epidermis in an umbrella-like fashion in other lesions. We believe that, in the present case, artificial sunlight therapy caused solar keratosis and that this developed into basosquamous carcinoma. To our knowledge, skin cancer developing after ultraviolet therapy with artificial sunlight without PUVA has not previously been reported in the English literature.

Incipient intraepidermal cutaneous squamous cell carcinoma: a proposal for reclassifying and grading solar (actinic) keratoses

Actinic keratoses (AKs) are primarily induced by ultraviolet (UV) radiation and are often identified as premalignant lesions. In our opinion, AKs are proliferations of transformed, neoplastic keratinocytes confined to the epidermis that may eventually extend into the dermis, at which point they are termed squamous cell carcinoma (SCC). In contrast to AKs, SCCs have the potential to metastasize and kill. This process is analogous to that of evolving carcinoma of the uterine cervix that has been termed cervical intraepithelial neoplasia (CIN), a time-tested and reliable classification that provides clinicians with accurate information on which to base treatment decisions regarding cervical neoplasms following biopsy testing. A similar classification scheme could provide guidance to clinicians for the diagnosis and treatment of evolving SCC of the skin and as such, we propose a similar classification using the terminology keratinocytic intraepidermal neoplasia (KIN). This system is more reflective of the histology and natural history of SCC and eliminates ambiguity in the terminology of lesions currently referred to as AKs. The KIN classification defines features by which individual specimens can be objectively graded and specific treatment recommendations are made based on the grade of the lesion. We propose that the term keratinocytic intraepidermal neoplasia (KIN) be used to define and describe evolving SCC of the skin and that the term actinic (solar) keratosis be eliminated.

The actinic keratosis. A perspective and update

BACKGROUND

Actinic keratosis (AK) is a common sun-induced precancerous neoplasm confined to the epidermis. It is the initial manifestation of a continuum of clinical and histologic abnormalities that progresses to invasive squamous cell carcinoma (SCC), a disorder that accounts for thousands of preventable deaths in America each year.

OBJECTIVE

The purpose of this work is to describe the actinic keratosis.

METHODS

This effort was performed by a literature review and analysis.

RESULTS

Like SCCs, the vast majority of AKs are asymptomatic. Although some actinic keratoses may become clinically inapparent, possibly either due to immune rejection or simply having their external surface unknowingly scraped off, an untreated AK represents a potentially curable fatal cancer.

CONCLUSIONS

Each AK should be treated before it progresses to invasive squamous cell carcinoma. Destructive modalities such as cryosurgery using liquid nitrogen and electrodesiccation and curettage are the mainstays of therapy. Each case must be individualized.

LEARNING OBJECTIVES

After studying this article, participant should be able to: 1. Understand the concept of an actinic keratosis. 2. Learn how to recognize its clinical manifestations. 3. Be aware of the danger it poses as an easily curable papulonodule that may become a fatal cancer.

Actinic keratoses. Differential diagnosis and treatment

Actinic keratoses are extremely common premalignant keratinocytic neoplastic lesions that develop primarily in fair-complexioned individuals during midlife or beyond. Genetic, occupational and other environmental factors predispose to the development of these lesions. Without treatment, a significant number may progress to fully developed neoplasms, especially squamous cell carcinoma, over a period of 20 to 50 years. The multistep theory of carcinogenesis is helpful in understanding the pathogenesis and progression of this important and highly prevalent lesion.

Premalignant keratinocytic neoplasms

Premalignant keratinocytic keratoses are common, especially in pale-complected persons in whom they appear most often as an actinic keratosis. Although the actinic keratosis has a very low malignant potential, arsenic, tar, thermal, scar, reactional, and radiation keratoses may be more clinically aggressive. This article discusses these premalignant keratinocytic neoplasms.

Proliferative actinic keratosis

BACKGROUND

Solar/actinic keratoses (AKS) are premalignant lesions, usually less than 1 cm in diameter, that appear on chronically sun-damaged skin.

METHODS

We describe four patients with a form of AK that enlarged and recurred despite standard treatment. Histologic examination revealed a single and multilayered sheet of anaplastic cells along the undersurface of the epidermis extending down hair follicles and present over a large area.

RESULTS

Three of the patients developed either a squamous cell carcinoma (SCC) or basal cell carcinoma (BCC) within the area encompassed by the AK.

CONCLUSIONS

These cases represent an insidious, proliferative form of AK with an increased tendency to develop into skin cancer.

Mutant p53 expression in solar keratosis: an immunohistochemical study

Thirty-eight solar keratoses from 32 patients were studied for expression of mutant p53 protein by an immunohistochemical technique. Twenty-eight of the 38 solar keratoses (73.7%) showed positive and variable nuclear labelling, whereas 10 specimens were immunonegative. The nuclear immunopositivity which was seen in all variants was mostly diffuse in distribution. The adjacent "normal" epidermis of 8 keratoses showed positive mutant p53 labelling. Eight of the keratoses were associated with invasive squamous cell carcinoma of which only two were immunopositive. Cytoplasmic labelling was never a feature. The study demonstrates that mutant p53 protein is commonly expressed in all variants of solar keratosis and that its expression correlates with atypical keratinocyte proliferation. It is proposed that the demonstration of mutant p53 in the adjacent normal epidermis may be a potential marker of early neoplastic transformation.

Hyperplastic acral keratoses--association with invasive squamous cell carcinoma

We have observed hyperplastic epidermal lesions in sun-damaged skin on the backs of the hands, wrists, and forearms that, in some examples, contain foci of invasive squamous cell carcinoma. Atypia in these lesions is focal or absent. Because of their bland histology, physicians are likely to interpret small or superficial biopsies as indicating a benign lesion. However, careful clinical correlation and follow-up are recommended, as residual tissue may contain invasive carcinoma or its precursor.

The diagnostic value of parakeratosis

A study of dermatopathological specimens exhibiting parakeratosis has been made and the parakeratosis classified on morphological and topographical criteria. Twelve patterns of parakeratosis have been identified and their association with particular pathological conditions described.

Persistent acantholytic dermatosis related to actinic damage

Ten male patients aged 38-63 years are presented, in whom a chronic, itchy, papular eruption developed on the upper trunk. Histology showed the characteristic features of Darier's disease. All the patients had clinical evidence of considerable solar damage and skin malignancies were frequently present. The condition is thought to represent a distinct entity which has been called persistent acantholytic dermatosis. The relationship between this condition, transient acantholytic dermatosis and actinic keratoses with Darier-like histology is discussed.

Evaluation of 5-fluorouracil in the treatment of actinic keratosis of the lip

Topically applied 5-fluorouracil has recently gained acceptance in the treatment of actinic keratosis of the lip; however, histologic evidence confirming the effectiveness of the therapy has not yet been established. Pretreatment biopsies were performed on six patients to confirm actinic damage and grade the degree of dysplasia. After 5-fluorouracil therapy, biopsies of tissue adjacent to the previous biopsy sites were performed to determine the success of treatment. Histologic evaluation showed residual dysplasia in all posttreatment biopsy material, even though the clinical stigmata of the actinic lesions had been improved or eliminated.

Apocrine acrosyringeal complex in the human skin

The acrosyringium of human apocrine sweat apparatus has been studied by light and electron microscopy using horizontal continuous serial sections. The apocrine acrosyringium is composed of 3 structurally different portions, a highly keratinizing upper portion, an incompletely keratinizing midportion, and a least keratinizing lower portion. Throughout these 3 portions, there are 2 distinctly different but closely inter-related cellular units, namely (I) a keratinization process lacking membrane-coating granules but containing keratohyalin droplets occurring in its inner cell layer, and (II) a keratinization process rich in membrane-coating granules and containing keratohyalin granules occurring in its outer surrounding concentric cell layers. In contrast to the inner cell layer, the outer cell layer does not belong to the duct proper but rather should be considered as the periacrosyringeal complex layer which is specially differentiated to envelop the intra-epithelial duct. This apocrine acrosyringeal complex in the hair follicle seems to be essentially similar to that of the eccrine apparatus in the epidermis.

Bowenoid transformation of seborrhoeic verrucae (keratoses)

Seborrhoeic verrucae (keratoses) are considered to be benign lesions. Occasional bowenoid transformation of these benign growths has not been widely recognized. Seven cases of seborrhoeic verrucae with bowenoid transformations are presented to alert the clinician and the pathologist to this occurrence.

Factors involved in skin carcinogenesis

A personal account of skin carcinogenesis is given based on forty years of investigation of normal and pathologic anatomy of the human skin. Symbiosis of acral portions of adnexa and of melanocytes with epidermal keratinocytes is stressed, and perversion of symbiosis to parasitism in tumor formation is discussed. The role of the basement membrane as a combined effort of, and filter between, ectoderm and mesoderm is stressed, and the nature of basal cell epithelioma as the least differentiated member of the tribe of fibroepithelial adnexal tumors is outlined. Experimental data supporting the promoting role of specific mesodermal stroma in basalioma formation and maintenance are presented.

[On the biologic phenomenon of epidermotropism (author's transl)]

The biologic phenomenon of epidermotropism is mirrored in the dynamic equilibrium between different cell types within the epidermis. In various pathological conditions, this balance may be upset, or foreign epithelial, neuroectodermal and mesenchymal tissue may selectively infiltrate epidermal or other epithelial structures. The importance of the concept of epidermal symbiosis in these conditions and resulting similarities in the clinical picture and biologic behavior are pointed out.